What works? No 23: Obesity

British adults and children are increasingly overweight - about 62% of men and 53% of women, according to latest figures. The rise is blamed on our increasingly sedentary lifestyle, as well as a more fatty diet. Children of obese parents are more likely to become obese themselves.

Health risks

Being overweight increases the risk of heart disease, diabetes, high blood pressure, gallstones and other diseases. Obesity shortens life expectancy. Even a modest weight loss - around 5kg (10lbs) - has important health benefits.

Losing weight

Exercise, diet, behavioural therapy and drugs are all effective to some degree but work best when used in combination. Combining a low-fat or low-calorie diet with increased exercise is likely to be better than dieting on its own. Taking fibre supplements may also help. There is no miracle diet or ideal exercise, although the Health Education Authority recommends that adults do 30 minutes of moderate to intense activity such as brisk walking or dancing every day. Behavioural treatment in classes or individual counselling sessions is also of little use on its own.

Drugs can help but two of the most popular appetite suppressants, fenfluramine and dexfenfluramine, were withdrawn in 1997 following concerns about heart complications. Anti-depressants such as Prozac have been shown to help in the short term - although they are not licensed for that purpose here - but all weight-loss drugs may have unpleasant side effects. When other approaches have failed, surgery - usually to reduce the capacity of the stomach - is effective. There has been insufficient research to test whether alternative therapies, such as acupuncture and hypnotism, really work. For children, reducing sedentary activity like watching television and playing computer games, is more effective than enforced exercise.

Sustaining weight loss

Most people regain the weight they have lost within a few months. Enlisting family members for support, as well as continuing contact with health professionals or other advisers, can help.

• What works? is based on reviews of the most up-to-date and reliable evidence available. It is written in collaboration with the NHS Centre for Reviews and Dissemination at York University (01904 433 634) and verified by experts.